Warning: Always make sure your work area is properly ventilated and know the materials you are working with.
NOTE: This is post from about 2013 that I am just now getting around to publishing. Please excuse any dated references.
I wanted to experiment with some vacuum forming at home and found a great Instructable (Here) by drcrash that I used as reference. I won’t replicate those instructions here because once you understand the basic idea, you really can create your vacuum forming rig however you’d like.
In a nutshell, you want a frame that can withstand high temperatures into which you will mount a piece of thermoplastic. For your base, you want an airtight (as much as possible) seal between your frame’s bottom and the orifice connected to your vacuum source. You heat the thermoplastic up until it is soft and pliable, then you pull the plastic over your desired object while the vacuum is running. You push your frame down against your seal and the air is evacuated around your part. The soft plastic is suctioned around your part, it cools, and you are left with a plastic shell of your desired object. That is all there is to it. The rest is just details about material selection, distributed airflow, proper sealing, and master part design considerations.
The materials are fairly inexpensive, I found the Instructable linked above to be fairly accurate regarding costs. Honestly though, you could make this rig even cheaper. Again, it is a simple concept that can be elaborated upon as far as your desire/pocketbook allows. Hack-sawing aluminum screen frame material is NOT the most ideal way to miter your corners. Mine came out pretty sloppy and if I were to make more frames, I’d use a band-saw with a jig.
Regardless of the pain that was my hack-sawing adventure, the frame still came out fairly good. Not a perfect frame by any means, but it pulls just fine in the final rig.
This is the entire rig fully assembled in my garage before it made its way into my kitchen for the actual vacuum forming process. I have a sample piece of plastic loaded into the frame ready to go. The hose coming out the bottom leads to my shop vac.
The photo above shows the small 3D printed part I prepped to be pulled. I was using this small dome for an LED enclosure of a small lighting project I was working on. The part is stuck to a small platform with some putty and this small platform is then resting on some folded mesh screen material. This allows the air to flow all around the part. The vacuum port is located beneath this mesh.
Ahh, the smell of fresh plastic in the oven. I keep all windows and doors open while I’m doing this to make sure my kitchen is properly ventilated. When the plastic starts sagging uniformly, it’s time to start the pull.
Final Verdict
If you don’t mind the smell, or have a spare oven lying around, this method works quite well. I wouldn’t suggest this for any production parts, but for roughing out an early concept or just validating a design before you pay to have someone else pull it for you, this is a very easy to do project at home/in the lab. Everything comes down to how good your seal is and how much vacuum pressure you have. My parts came out decent enough for the molds I was working on, but there was definitely loss of detail in some finer features. I recommend any hobbyist / professional designer have this skill in their tool belt. It doesn’t have to be perfect, sometimes, you just need a vacuum formed part today.